WLAN摆脱线缆羁绊

无线局域网WLAN技术发展至今,主要分为两大协议体系;IEEE 802.1协议标准体系和欧洲ETSI BRAN制定的HiperLAN协议标准体系。HiperLAN2工作在5GHz频段,工作速率可达54Mbps。IEEE 802.11,802.11a和802.11b是IEEE已经颁布的WLAN的标准协议,该标准定义了WIAN物理层(PHY,Physical Layer)和介质访问控制(MAC,Medium Access Costrol)的规范。目前WLAN中应用最为广泛和成熟的是IEEE 802.11b局域网体系。     

基于IEEE 802.11bWLAN安全技术研究

随着无线局域网(WLAN)技术的迅速发展,其安全问题日益受到人们的关注.由于传输的特殊性,WLAN始终面临严峻的安全考验.无线网络攻击技术的不断翻新,基于IEE 802.11b的攻击技术会越来越多,复杂性将越来越高.所以与有线网路相比,保护WLAN安全的难度要远大于保护有线网络.文中介绍了基于IEEE 802.11b协议下的WLAN可能面临的非法登录、拒接服务、字典攻击等安全威胁,分析了如何提高WLAN下的几种安全机制及802.11协议下的802.11i安全标准.提出了现有无线设备使用中一些可提高WLAN安全性的解决措施,在一定程度上提高了WLAN的安全性.     

基于IEEE802.11b WLAN安全技术研究

随着无线局域网（WLAN）技术的迅速发展,其安全问题日益受到人们的关注。由于传输的特殊性,WLAN始终面临严峻的安全考验。无线网络攻击技术的不断翻新,基于IEE802.11b的攻击技术会越来越多,复杂性将越来越高。所以与有线网路相比,保护WLAN安全的难度要远大于保护有线网络。文中介绍了基于IEEE802.11b协议下的WLAN可能面临的非法登录、拒接服务、字典攻击等安全威胁,分析了如何提高WLAN下的几种安全机制及802.11协议下的802.11i安全标准。提出了现有无线设备使用中一些可提高WLAN安全性的解决措施,在一定程度上提高了WLAN的安全性。     

WLAN走向安全、高速、互联

作为全球公认的局域网权威,IEEE 802工作组在过去20年中制定的系列标准在局域网领域内独领风骚。这些协议囊括了802.3Ethernet协议、802.5 Token Ring协议、802.3z 100BASE-T快速以太网协议。经过了数年酝酿之后,在1997年,IEEE发布了802.11协议,这也是在无线局域网(WLAN)领域内的第一个国际上被广泛认可的协议。随后,802.11a、802.11b、802.11d标准相继完成。目前正在制订的一系列标准有802.11e、802.11f、802.11g、802.11h、802.11i等,它推动着WLAN走向安全、高速、互联。     

改进基于WEP协议的无线局域网的安全

目前的无线局域网(WLAN)都支持IEEE.802.11和802.11b标准,这些标准都以WEP(Wired Equivalent Privacy)协议为基础来进行加密和认证.分析了WEP协议存在的安全漏洞,为架设更高服务质量的WLAN提出了一种安全改进的方案.     

无线ATC中802.11b信道编码系统的改进

IEEE802-11b是现在应用最广泛的无线局域网协议,带宽只有83.5MHz.为了达到较高的数据传输率,它只采用了CRC-32(循环冗余检验码),而并没有采用其它差错控制编码.当信道环境不理想时,误码率很高,QoS性能没有保证.无线ATC的数据传输率很低,但对QoS性能要求却很高.根据这些特点,本文对要传输的信息增加差错控制编码,提出了具体的编码方案.仿真实验表明,改进之后,IEEE802.11b的QoS性能得到了显著地提高.     

无线局域网中的认证机制

当前无线局域网(WLAN)主要的认证技术包括了IEEE 802.11中的开放系统认证和共享密钥认证,IEEE 802.11i中的802.1x认证协议,以及我国的无线局域网安全标准WAPI中的WAI认证机制.概述了以上各种认证机制,讨论了它们各自的优缺点,并根据其存在的安全漏洞,给出了两种改进方案.最后给出了WLAN认证机制的进一步研究方向.     

移动PC无线上网的实现

本文从分析IEEE802.11协议入手,列举若干种无线上网的方式并在此基础上详细阐述WLAN(无线局域网)的实现方式。     

基于无线信道的冲突分解算法仿真研究

目前,无线局域网(WLAN)中的媒体接入控制层(MAC)广泛采用基于IEEE802.11的二进制指数回退算法(BEB)的DCF协议.当WLAN中的节点数目迅速增加时,该协议存在系统吞吐量会急剧降低,网络性能变差的缺点.详细分析了无线局域网中IEEE 802.11MAC层的二进制退避协议,指出原协议在进行冲突处理上的不足,并结合树型分解算法(TSA)和快速分解算法(FCR),提出一种改进的树型冲突分解算法(ITSA).并用MATLAB仿真了CSMA/CA协议和ITSA算法.分析和仿真结果证明,与IEEE 802.11等协议采用的二进制指数退避算法相比,该算法能较大的提高系统吞吐量.     

共享WiFi系统中MAC层快速切换方案的研究与实现

基于IEEE 802.11协议的无线局域网(WLAN)能够为无线多媒体应用提供足够的带宽,由于无线接入点AP(Access Point)发射功率受限,其服务覆盖范围也因此受限,这使得终端在移动过程中需要在不同AP之间频繁地切换,由此带来的时延严重影响了无线多媒体应用的服务质量。因此,提出一种基于信道掩码和优先级的选择扫描策略和选择性邻居图缓存算法,增大了命中缓存的概率,减少了扫描的信道数量和系统信令开销。仿真结果表明,该切换方案可以有效降低移动节点MN(Mobile Node)在共享WiFi(Wireless Fidelity)系统中不同AP间的切换时延,满足了无线多媒体业务(如VoIP)的传输要求。     

Wireless GINI: an educational platform for hosting virtual wireless networks

We describe Wireless GINI, a wireless platform for hosting virtual networks. Wireless GINI Is Not Internet (GINI) allows each virtual network to define its own topology and network configuration, while amortizing costs by sharing the physical infrastructure. The platform also creates mechanisms to readily integrate physical wireless devices into a deployed network. The platform supports a diverse combination of network elements that are all integrated into one custom Internet. The platform seamlessly integrates process‐emulated components running on the user machine, wireless mesh overlays deployed on the wireless platform, and generic wireless devices connected to the user's custom network. Wireless GINI provides a user‐friendly interface that makes the physical setup process completely transparent to the user. A centralized server is used to provide this transparency, handle user requests, and automatically provision the shared physical infrastructure. We describe the design and implementation of Wireless GINI. Moreover, we evaluate the performance of the platform and suggest several educational experiments that can be conducted on this new platform. A detailed survey of the existing toolkits and platforms and a comparison with Wireless GINI are also provided. Copyright © 2016 John Wiley & Sons, Ltd.     

Wireless Security — what is out there?

Frost & Sullivan have recently released a report on the European Wireless Security Market and this has revealed some interesting findings with regards to wireless security. A selection of technologies that can be deployed to secure wireless environments are examined below, including the wireless transport layer security (WTLS), virtual private networks (VPN), wireless public key infrastructure (WPKI) and authentication systems. It is vital to ensure that all parts of the wireless security framework are secured, including mobile devices, wireless transmissions and networks, gateways and servers, and backend systems.     

Design and implementation of a smart system for personalization and accurate selection of mobile services

Wireless mobile services are computing applications that run on handheld wireless devices. Such applications must work within the daunting constraints of the devices, which include memory, processing power, input capabilities, and size of display. It is therefore important that mobile services take into account the user’s context, optimize resource usage, and minimize input effort imposed on the user. In this paper, we present the design and implementation of a smart agent-enabled system for personalizing wireless mobile services and advertisements for Java 2 Micro Edition (J2ME) or Java ME, and Wireless Application Protocol (WAP) enabled devices. We use software agents for context filtering because such autonomous software entities have characteristics that can benefit mobile devices and the wireless environment, and the Composite Capability/Preference Profiles (CC/PP) standard for defining profiles for user preferences and device capabilities. The system incorporates the use of artificial neural networks to adaptively and iteratively learn to select the best available service based on contextual information. The system is evaluated using practical operating scenarios, as well as empirical data and results show an 87% success rate in the selection of the best available service.     

Handheld Librarians: A Survey of Librarian and Library Patron Use of Wireless Handheld Devices

ABSTRACT

Wireless technologies are becoming more prevalent in American society, but are they in our libraries? This article is a result of a survey of 766 librarians (mostly academics) across the United States on their use and perceived use of their customers of personal digital assistants (PDAs), smartphones, webpads, and other handheld wireless devices. How are these devices being used? What percentage of libraries support wireless handheld device users, and how is this support delivered? Is there a demand for more services for these users and for what are they asking? Have libraries modified content to meet the needs of wireless handheld device users, and if so, what content have they changed? Last, what are librarians’ perceptions of wireless handheld devices and the cost and licensing of wireless content?     

Wireless advertising's challenges and opportunities

Rapidly developing wireless net-working technology and the growing mobile-device user base have fueled interest in activities that deliver advertisements to mobile devices over a wireless network. Studies by wireless media research companies indicate that delivering permission-based alerts to wireless phones captures consumers' attention, drives response actions, and builds brand awareness. Wireless devices are accessible, personal, and location aware. These characteristics allow for highly targeted, flexible, and dynamic wireless advertisements. Yet the target audience is vast, and users must be able to search for information, issue inquiries, and make purchases at any mobile location.     

The hard road ahead for WAP

Recent "digital home" and "digital office" demonstration projects by Cisco, Sun Microsystems, and others have shown, that we are on the verge of wiring pretty much everything we can into Internet-capable networks. Similarly, all the recent market enthusiasm for WAP (Wireless Application Protocol) foreshadows a coming boom in networking wireless devices. Or does it? The author discusses the fact that although the Wireless Application Protocol shows great promise, to succeed it must overcome many inherent limitations.     

现场级无线网络体系结构

本文概要地介绍了工业控制系统的发展历史，并通过对无线通信技术的分析研究，提出了一种现场级无线网络体系结构．本文还介绍了一种遵从上述体系结构的无线网络的实现方法．实验证明上述体系结构设计合理，可以满足现场级无线设备的通信要求．     

A Survey on Wireless Grid Computing

Wireless Grid computing extends the traditional Grid computing paradigm to include a diverse collection of mobile devices enabled to communicate using radio frequency, infrared, optical and other wireless mechanisms. Among the devices coming into use in wireless grid implementations are tiny sensors, Radio Frequency Identification tags (RFID). Personal Digital Assistants (PDAs) and paging devices, cellular phones, hand-held or wearable computers, laptop computers and special purpose computers embedded into many modern appliances [8, 26, 29]. Though many of these devices were initially developed to serve a specific, autonomous purpose, their potential for cooperation through the sharing of resources and capabilities, and the massive amounts of resources available due to their numbers, is quickly leading to applications resembling traditional Grid computing. This paper presents a survey of the current state of wireless grid computing. This includes a discussion of the cooperation between wired and wireless grids including ways in which wireless grids extend the capabilities of existing wired grids. It also discusses many of the new capabilities and resources available to wireless grid devices and a sampling of several applications of these new resources. It provides a sampling of many current research endeavors in the wireless grid arena and an examination of a number of the potential challenges resulting from the unique characteristics of wireless grid devices.     

体内植入装置的磁耦合谐振无线电能传输分析

体内植入医疗装置已被广泛应用,然而使用传统的供电方法为其供电却极为不便。磁耦合谐振式无线电能传输通过近场区强耦合谐振实现能量的高效传输,为体内植入医疗装置的供电提供了有效途径。介绍了体内植入式医疗装置的磁耦合谐振式无线电能传输原理,阐述了无线电能传输技术的理论基础耦合模理论（ CMT）,并基于该理论仿真研究了磁耦合谐振式无线电能传输技术高效传输的必要条件。     

Privacy and Security in Wireless Computing

It has typically been the case that individuals build networks first, and deal with security issues later. Wireless is no exception. In a world where security is still advertized as being achievable through the use of disparate products, it is no surprise that the mistakes encountered in wired computing are now appearing in the wireless environment. Industry has rushed to bring wireless phones, personal digital assistants (PDAs), pagers, wireless laptops, smart phones and other handheld devices to eager consumers. However, market demands for new and easier access have encouraged manufacturers to accelerate production of wireless applications with little attached priority to security and privacy issues.